In modern microelectronics, electronic components are often labeled for their identification. However, some components present, as the external layer of the component casing, a low-contrast or transparent layer, for example, filled reaction resins (glob top), glass, quartz, etc. It is very difficult to apply a text by laser with such components because the surfaces of such components after laser irradiation do not present sufficient contrast to be recognized using common optical systems.
Moreover, conventional laser labeling on mold or glob top compositions have a penetration depth greater than 15 μm, up to approximately 70 μm. This means that more than 70 μm of ablatable or inscribable material thickness must be present to prevent damage caused by the laser to the chip to be labeled. Accordingly, the minimum required component height increases to greater than 70 μm.
To circumvent this problem, an additional labeling film is frequently applied by lamination to the component surface, which film presents a higher contrast value after laser labeling. Besides the contrast layer, such a film also usually presents an adhesive layer, resulting then in a total thickness greater than 20 μm, which amounts to a considerable contribution to the total thickness (height) of the component in miniaturized components.
In the case of components that have very stringent requirements for a (small) component height, this method is thus not the optimal solution. In addition, with some components, unavoidable difficulties arise to an extent due to the film lamination and the associated processes. Thus, for example, an adhesive film may become detached, particularly after sawing processes to separate the components that have been produced simultaneously and in parallel on a wafer. In the case of materials that present, between the film and the substrate of the component, a thermal expansion coefficient that is not adjusted, strong additional stresses can occur in the substrate and in the casing, which limit the lifespan of the component and can even lead to premature failure or malfunction.
Another possibility of laser labeling consists in applying one or more thin conducting metal layers to the surfaces of such components, which surfaces present contrast between each other and with respect to the substrate, and in labeling them with a laser by ablation. Such a labeled coating, however, cannot be used with electromagnetically sensitive components, such as SAW and FBAR components, because the metal layer used interferes considerably with the functioning of such components as a result of capacitive coupling with the active structures of the component.